Here is my attempt to combine two projects. One is User Interface for lathe Grbl on mega2560 + reprap smart display controller by bdurbrow. https://github.com/bdurbrow/grbl-Mega Second is threading G33 support by MetalWorkerTools. https://github.com/MetalWorkerTools/grbl-L-Mega There is some iformation about projects on their wiki pages.
Video of components used https://youtu.be/8M4gzLkSXls Video shows assembled dewise https://youtu.be/N7hlYoIhV2g Short test video https://youtu.be/dcXR74F-ByY
I have changed many minor issues in bdurbrow, but I still have couple there not solved yet. Here is description and discussion MetalWorkerTools/grbl-L-Mega#4
Pressing PartZero button now zeroing axis in active coordinate system position, not machine position. tool_length_offset aplied if any. smartZeroDiameter applied, but I dont use it on lathe (its zero all the time) so didnot check it.
Pressing shiftedPartZeroKey zeroing Machine position with tool offset.
Use NC swithes with RC filter